Specs:

Intel Pentium B690 2.2GHz dual core, with Intel HD2000 IGP

8 GB RAM

Only mods I'm running are OOO and the OOO-compatible version of MMM. I have the graphics settings quite low.

I'm getting huge performance hits, especially when facing large groups of NPCs, regardless of whether they're visible on screen or obscured by a wall or something. Sometimes, though, it happens when I'm... not facing anything particularly demanding, like a stack of boxes.

My system runs New Vegas fine and I'm pretty sure that's a more system intensive version of the same engine.

Any ideas what might be going on?